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authorBin Meng2018-10-24 08:36:40 -0500
committerSimon Glass2018-11-14 11:16:28 -0600
commit1a6bd4717fe68ca212abca21a0e08af186fdb442 (patch)
tree3d3d9d6ad45b88c9525fcf56772ed56728a12ddb
parent8ee27da343aac7ba88b1efab620fc5ef30325ded (diff)
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dm: doc: Update description of pre-relocation support
Add some description about pre-relocation driver binding, including usage of DM_FLAG_PRE_RELOC flag and caveats. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Simon Glass <sjg@chromium.org>
-rw-r--r--doc/driver-model/README.txt16
1 files changed, 12 insertions, 4 deletions
diff --git a/doc/driver-model/README.txt b/doc/driver-model/README.txt
index 36541630a2..07b120d512 100644
--- a/doc/driver-model/README.txt
+++ b/doc/driver-model/README.txt
@@ -830,10 +830,18 @@ Pre-Relocation Support
830---------------------- 830----------------------
831 831
832For pre-relocation we simply call the driver model init function. Only 832For pre-relocation we simply call the driver model init function. Only
833drivers marked with DM_FLAG_PRE_RELOC or the device tree 833drivers marked with DM_FLAG_PRE_RELOC or the device tree 'u-boot,dm-pre-reloc'
834'u-boot,dm-pre-reloc' flag are initialised prior to relocation. This helps 834property are initialised prior to relocation. This helps to reduce the driver
835to reduce the driver model overhead. This flag applies to SPL and TPL as 835model overhead. This flag applies to SPL and TPL as well, if device tree is
836well, if device tree is enabled there. 836enabled (CONFIG_OF_CONTROL) there.
837
838Note when device tree is enabled, the device tree 'u-boot,dm-pre-reloc'
839property can provide better control granularity on which device is bound
840before relocation. While with DM_FLAG_PRE_RELOC flag of the driver all
841devices with the same driver are bound, which requires allocation a large
842amount of memory. When device tree is not used, DM_FLAG_PRE_RELOC is the
843only way for statically declared devices via U_BOOT_DEVICE() to be bound
844prior to relocation.
837 845
838It is possible to limit this to specific relocation steps, by using 846It is possible to limit this to specific relocation steps, by using
839the more specialized 'u-boot,dm-spl' and 'u-boot,dm-tpl' flags 847the more specialized 'u-boot,dm-spl' and 'u-boot,dm-tpl' flags